A number of methods for preparing specimens for microscopic analysis of fiber cross-sections are known. Olson, et al., American Dyestuff Reporter, March 1972, p. 58, describes a method in which a crimped yarn is mounted on a frame under tension sufficient to remove the yarn crimp, and the frame is placed into a capsule with a cureable resin to obtain an embedded yarn sample for cross-sectioning with a microtome. Cemel, et al., U.S. Pat. No. 4,233,363 discloses a procedure whereby a crimped yarn is mounted on a frame under tension and the samples dipped into a lacquer to freeze the filaments in their relative positions. The sample is then cut and mounted in a holder. Nelson, U.S. Pat. No. 4,790,132 describes a method whereby a crimped yarn is hung on a rack hook and sufficient weight is added to the yarn to pull out the crimp. Acrylic lacquer is applied dropwise to the yarn, the sample is allowed to dry and is placed in a mold cavity where it is embedded in epoxy. None of these methods discloses a means for aligning the decrimped yarn sample within the sample holder during the embedding process.
Synthetic fibers are produced having a wide range of cross-sections in order to achieve specific physical effects such as hand, luster, and soil-hiding in substrates made from the yarns. In many instances, in order to characterize a yarn sample, it is desirable to obtain a true cross-section of the filaments which make up the yarn bundle so that a microscopic analysis of the cross-section can then be made. By true cross-section, it is meant the cross-section taken at right angles to the longitudinal axis of a filament. In a multifilament crimped yarn, all of the filaments must be decrimped and approximately aligned in a parallel orientation within the yarn bundle in order to cross-section the sample perpendicular to all of the filaments in the yarn bundle.
The above-mentioned methods provide means for decrimping and aligning filaments within a yarn sample prior to embedding in a resin in a sample container, but the orientation of the decrimped yarn bundle in the sample container i$ not controlled If the yarn bundle is not aligned parallel to the axis of the hardened resinous stub, it is necessary to align the yarn bundle which is embedded in the resinous specimen perpendicular to the microtome blade. Such alignment may be difficult to effect accurately because the end of the stub is often facetted by trimming prior to sectioning, making viewing of the yarn bundle difficult. Difficulties in viewing the embedded yarn bundle also can arise due to opacity of the embedding resin used.